In a large bowl, put 1 tablespoon of tom yum paste. Add lime and fish sauce and stir. If you have a clear soup broth handy, add a little bit of soup broth to increase the liquidity. Add a tablespoon of milk. Stir all the salad ingredients. Give it a blast in microwave for 30 seconds.
Finely cut lemongrass. When you cut lemongrass, it will come out in circles. Cut red onion and finely cut lime leave. When you cut lime leave, fold the leave tightly before you cut.
Add chopped lime leaves, red onion and lemongrass into a bowl with the sauce. Mix all the ingredients well.
Boil water in a pot. Once the water is boiled, place the prawns and just when the prawns turn red, drain the prawns. Place the prawns inside the mixing bowl with the salad sauce. Mix well and it's ready to serve.
Don't over cook the prawns. This dish is best with rice. Add chili padi if you like a spicier taste.